Growth in the semiconductor fabrication industry over the last thirty years has averaged about fifteen percent. This growth has also dictated high capital costs with short obsolescence times which places intense pressures upon the fabricators to increase productivity. Certain technology enhancements, for example copper metal layers and interconnects, while providing superior device performance and simplified structures, come with logistical penalties due to complexities in device manufacture thus making productivity gains even more difficult.
Automation of material handling is becoming more critical in the industry as it strives for increased productivity. Most manufacturers employ some level of automated intrabay handling and some employ automated interbay transfer of wafers to process tools. Industry consortia have developed various standards for next generation 300 mm wafer fabrication operations, for example, standardized carriers and loadports. Automated material handling systems including hoists and overhead transports are capable of delivering front-opening unified pods (FOUP) directly to load ports.
Material execution systems (MES) and material control systems (MCS) are widely used by integrated circuit fabricators to track process and logistical attributes of the manufacturing operations. MES systems generally determine where material should go and when it should go there, while MCS generally determines how material should get to its determined destination and then manages its transportation. In some systems, there is no MES; rather, operators request material transfers from an MCS interface. MES and MCS also interface with other enterprise systems on one hand and industrial process systems on the other hand. Significant gains in utilization of operational assets have been realized by the adoption of MES and MCS. More specifically, MES and MCS enable critical data collection, process management, maintenance management, and WIP tracking and genealogy. Production and parametric data associated with WIP is used to populate database records for real time in-process or historical usage. The data may be collected on the factory floor or automatically from process equipment. Process management aspects of MES and MCS enable automatic corrections in sophisticated, highly automated systems or provide decision support to operators for correcting and improving in-process activities. Maintenance management of course tracks and directs activities to maintain equipment, tools and carriers. The product tracking aspects enables snap shot visibility of where WIP resides and status information as well as WIP material supplier, lot information, customer data, serial numbers, current production conditions and alarms or flags signaling rework or other exceptions related to the WIP.
Carriers for transporting, storing and processing wafer cassettes are employed in microchip fabrication and continue to play a more important role in the quest for completely automated and integrated manufacturing. Information corresponding to the wafers in a particular carrier is commonly stored in an electronic data card mounted to the container. The data card is adapted to store process and equipment data corresponding to the wafers within the associated container and the associated container and its WIP. Furthermore, the data card may be adapted to interface electronically with each processing station when the container is engaged with the processing station. Such interfacing provides for the two-way transfer of data between the data card and a local controller associated with the processing station. The local controllers may be networked to communicate with MES and MCS. A display associated with each local controller may display data read from the data card mounted to the carrier that is then currently engaged with the corresponding station. The data card may itself include alphanumeric display means such as a liquid crystal display for the display of the information stored therein. Typically, data is stored and displayed in a certain number of rows of a certain number of characters, for example fourteen rows of sixteen characters each. An operator may request display of the information by pressing buttons located on the face of the data card. Limited display space on the display means requires toggling through lines of stored data to find the data of interest to the operator. This is the typical manner in which any data stored on the data cards is retrieved. Limited battery capacity of the data card necessitates operator requests to display the data and further necessitates automatic display disablement between such requests to prevent battery depletion during extended periods of storage. Batteries that have to be replaced while a carrier is in process causes disruption to the production schedule and material flow. Furthermore, as automated material handling systems become more commonplace, the operator will have less opportunity to access such data cards and shorter intervals when access is available. Additionally, such data cards are not always compatible with all processes carried out. For example, carrier immersions for clean and rinse operations require the laborious removal of data cards from the carrier. Data cards are expensive and costs are multiplied by the number of carriers in a fabricator's process.
High equipment utilizations, logistical complexities related thereto and to new process requirements, larger and heavier carriers (particularly with next generation 300 mm fabrication), and trends toward complete automated handling systems all result in less operator handling of work in process (WIP) without interfering with and interrupting material flow. Any interruption of WIP by an operator is more undesirable as less opportunity for such interruptions without cascading process effects are available in a tightly controlled and scheduled fabrication process. However, it remains necessary that the operator be able to identify WIP and to be timely apprised of the various process and equipment information related thereto. It is also desirable that the operator remains aware of various process and logistical attributes of the manufacturing operation.